In recent years, computer environments for hardware and software have been improving significantly. In particular, services such as dedicated terminals for electronic books and content distribution are prevailing which had previously been impractical due to inadequate processing performance and insufficient storage capacities. New applications used for such services include contents collaborating with a text-to-speech function and contents with text-to-speech voice data embedded therein.
Furthermore, the service for electronic books as described above can be applied to books such as paper documents stored in libraries. Electronic data on a paper document can be obtained by, for example, converting the paper document into electronic data with a quality appropriate for mechanically reading the document aloud or creating text-to-speech voice data corresponding to the paper document.
However, misconversion may be included in an operation of obtaining text-to-speech voice data by converting a paper document into electronic data, and thus, the electronic data and the text-to-speech voice data may need to be corrected. A technique for correction is, for example, to detect and correct defective portions in a text-to-speech voice.